Chart of global temperature since 1950, also showing the phase of the El Niño-La Niña cycle. Via NASA.

Signs are increasingly pointing to the formation of an El Niño in the next few months, possibly a very strong one. When combined with the long-term global warming trend, a strong El Niño would mean 2015 is very likely to become the hottest year on record by far.

El Niño visualization (via NOAA)

An El Niño is “characterized by unusually warm ocean temperatures in the Equatorial Pacific,” as NOAA explains. That contrasts with the unusually cold temps in the Equatorial Pacific during a La Niña. Both are associated with extreme weather around the globe. But, as the above chart from NASA shows, El Niños are generally the hottest years on record, since the regional warming adds to the underlying global warming trend. La Niña years tend to be below the global warming trend line.

Because 1998 was an unusually strong “super El Niño,” and because we haven’t had an El Niño since 2010, it can appear as if global warming has slowed — if you cherry-pick a relatively recent start year. But in fact several recent studies have confirmed that planetary warming continues apace everywhere you look.

Remember that 2010, a moderate El Niño, is the hottest year on record so far. And 2010 saw a stunning 20 countries set all-time record highs, including “Asia’s hottest reliably measured temperature of all-time, the remarkable 128.3°F (53.5°C) in Pakistan in May 2010.” Meteorologist Dr. Jeff Masters said 2010 was “the planet’s most extraordinary year for extreme weather since reliable global upper-air data began in the late 1940s.”

Given that the “Earth’s Rate Of Global Warming Is 400,000 Hiroshima Bombs A Day,” the planet is half a billion Hiroshimas warmer than it was in 2010. So even a moderate El Niño will cause record-setting temperature and weather extremes. But a strong one, let alone a super El Niño, should shatter records.

Peru’s official El Niño commission said last week that they are expecting an El Niño to start as soon as April. Peru tracks this closely because “El Nino threatens to batter the fishmeal industry by scaring away abundant schools of cold-water anchovy.”

To be clear, an El Niño is not a sure thing at this point. Some forecasters put the chances at about 60 percent, but one recent study put the chances at 75 percent.

Roundy said the chances of an unusually strong El Niño event “Are much higher than average, it’s difficult to put a kind of probability of it … I’ve suggested somewhere around 80%”

“The conditions of the Pacific ocean right now are as favorable for a major event as they were in march of 1997. That’s no major guarantee that a major event develops but clearly it would increase the likelihood of a major event occurring,” Roundy says.

The El Niño Southern Oscillation (ENSO) doesn’t change the overall warming trend, but it is a short-term modulation, what NASA labels the largest contributor to the “natural dynamical variability” of the climate system. El Niño and La Niña are typically defined as sustained sea surface temperature anomalies (positive and negative respectively) greater than 0.5°C across the central tropical Pacific Ocean. You can read the basics about ENSO here.

One key El Niño indicator is the rapid rise in upper ocean temperatures in the central and eastern Pacific — just what NOAA reported Monday:

Since the end of January, temperature anomalies have strongly increased.

Meteorologist Michael Ventrice had a detailed analysis in late February here on why such warming is significant.

For El Niño junkies, NOAA’s National Centers for Environmental Prediction (NCEP) releases a weekly ENSO report every Monday here. And super-junkies can go to the ENSO page of the Australian government’s Bureau of Meteorology (updated every second Tuesday), which also charts another key El Niño indicator, the Southern Oscillation Index (SOI). For the SOI, “sustained negative values below −8 may indicate an El Niño event.” The latest 30-day SOI value (through March 23) is −12.6.

The ensemble mean prediction of NCEP’s Climate Forecast System (CFS) is for an El Niño in early summer, eventually getting quite strong:

When the El Niño forms and then peaks is crucial to whether 2014 or 2015 (or both!) will be the hottest year on record. A 2010 NASA study found “the correlation of 12-month running-mean global temperature and Niño 3.4 index is maximum with global temperature lagging the Niño index by 4 months.”

If we do get an El Niño, and it looks anything like the 1997/1998 one, then 2015 in particular should be the hottest year on record by far. Stay tuned.

Joe Romm is a Fellow at American Progress and is the editor of Climate Progress, which New York Times columnist Tom Friedman called "the indispensable blog" and Time magazine named one of the 25 "Best Blogs of 2010." In 2009, Rolling Stone put Romm #88 on its list of 100 "people who are reinventing America." Time named him a "Hero of the Environment″ and “The Web’s most influential ...

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Upper-Ocean heat is moved to depths of as much as 1000 meters by ocean thermal energy conversion using a heat pipe or deep water condenser design. As the MIT article, How the ocean reins in global warming, points out, this would delay long-term global warming, even as it could produce as much energy as is currently derived from fossil fuels.

Jim, agree this is a potential however would have to ask what would the effect(s) be in the future. I could see the disruption of ocean gyres or the upwellings of high nutrient cold waters just off the cuff. Would we be substituting one problem for another? Let's not repeat the lack of forsight as with fossil fuels. By all means investigate this as a potential resource but look at the repercussions first.

Max, the method I propose does not upwell cold water. It takes the surface heat to the depths the same way the air conditioning system in your car removes heat to the exterior. See recent post here. This can rein in global warming as has been demonstrated by the recent hiatus, which was brought about when strong trade winds moved heat to between 100 and 300 meters in the Eastern Pacific. OTEC would move the heat at least 3 times as deep and therefore would keep it there long enough for atmospheric CO2 levels to decline. This is a positive outcome we in Canada should be promoting but of course that is not the case.

Jim, am aware of the direction of heat transfer. If heat transferred to the cold depths my question is what would the effect be. Those 2 were just things I could readily envision off the top of my head. In other words lets figure out the repercussions before jumping in the deep end. Am sure the 1st users of fossil fuels never figured they could damage the global environment. Who knows, this idea could be a good thing but am concerned about unforseen repercussions. Would hope our current situation would have taught us to look before we leap so to speak. Have the effects of such a heat transfer been modelled? I know the trades are buffering atmospheric temperatures right now but will this increase oceanic dead zones, create algal blooms etc.... Should definitely be investigated but cautiously so as not to worsen a bad situation.

Max, there doubtlessly would be thorough investigation before OTEC was implemented on any kind of scale that could have significant impact. So far though it is seems like the only rationale way we can produce energy that undoes the effects of global warming. So far there is no investigation going on in relation to the deep water condenser design, which would produce the benefits I am convinced could be forthcoming and this, to my mind, is troubling.

Considering the projected size of the economic impact from AGW these possibilities should at least be modelled! It sounds promising. The models for oceanic effects are probably not as developed as those for atmospheric effects though. A possibility to look into.